Although purchasers, regulators, and advocates exert considerable pressure on care delivery organizations to improve the quality of health care services, few approaches to quality improvement (QI) have been rigorously demonstrated to improve care. Information is particularly needed on the relative effectiveness and cost- effectiveness of different approaches to improving outpatient care. We propose to take advantage of the planned initiation of a disease management program for childhood asthma in a Boston-based integrated delivery system by simultaneously implementing an office-based QI strategy in different practices in the same system, and to assess via a randomized design their relative effectiveness and cost-effectiveness in improving processes and outcomes of care. After each intervention has been in place for one year, we will offer the complementary intervention to the practice, to determine the marginal benefits and costs that each approach offers. Data will be derived from a parent telephone survey, a provider survey and a computerized claims databases for those children in the integrated delivery system with asthma who are covered by one of three large managed care organizations. The specific aims of the study are to: 1. establish a practice based quality improvement program in a large managed care organization, 2. determine how this strategy, when compared with a disease management strategy that targets high cost patients, affects specified processes of care, health care outcomes, and health care costs for children with asthma, and 3. assess the relative cost-effectiveness of these two approaches.